# What You'll Need:
→ Pasta
01 - 12 oz egg noodles
→ Seafood
02 - 2 cans (6 oz each) tuna in water, drained
→ Vegetables
03 - 1 cup frozen peas, thawed
04 - 1 small onion, finely chopped
05 - 2 cloves garlic, minced
06 - 1 cup sliced button mushrooms (optional)
→ Sauce
07 - 2 tablespoons unsalted butter
08 - 2 tablespoons all-purpose flour
09 - 2 cups whole milk
10 - ½ cup sour cream
11 - 1 teaspoon Dijon mustard
12 - ½ teaspoon salt
13 - ½ teaspoon black pepper
14 - ½ teaspoon dried thyme
→ Cheese
15 - 1 cup shredded cheddar cheese
→ Topping
16 - 1 cup crispy fried onions
# Step-by-Step:
01 - Preheat oven to 375°F. Lightly grease a 9 x 13 inch baking dish.
02 - Prepare egg noodles according to package instructions until al dente. Drain and set aside.
03 - In a large skillet over medium heat, melt butter. Add chopped onion and mushrooms; sauté for 4 to 5 minutes until softened. Add garlic and cook for an additional minute.
04 - Sprinkle flour over vegetables and stir constantly for 1 minute. Gradually whisk in milk, continuing to stir until sauce thickens, about 3 to 4 minutes.
05 - Remove skillet from heat and stir in sour cream, Dijon mustard, salt, black pepper, and dried thyme.
06 - Fold drained tuna, peas, shredded cheddar, and cooked noodles gently into the sauce until evenly incorporated.
07 - Transfer mixture into the prepared baking dish and spread evenly.
08 - Evenly distribute crispy fried onions over the casserole surface.
09 - Bake uncovered for 25 to 30 minutes, until mixture is bubbly and topping is golden brown.
10 - Allow casserole to rest for 5 minutes before serving.
